FireEye today said that nation-state hackers breached its network by inserting malicious code into a SolarWinds software update.

The security vendor first disclosed that it was hit by a “highly sophisticated” nation-state attack targeting its government customers last week. While FireEye hasn’t yet named Russia in the attack, on Sunday multiple news outlets blamed Russia government hackers, nicknamed APT29 or Cozy Bear, for the breach and said they also hit the U.S. Treasury and Commerce departments, along with other U.S. government agencies.

Late Sunday, SolarWinds issued a security advisory about the supply chain attack on its Orion Platform software update issued between March and June. “We have been advised this attack was likely conducted by an outside nation state and intended to be a narrow, extremely targeted, and manually executed attack, as opposed to a broad, system-wide attack,” the advisory said.

SolarWinds recommended that customers upgrade to the latest version of the Orion platform.

In its alert, FireEye said that the SolarWinds supply chain attack hit “multiple organizations” dating back to the spring, and it’s working to notify those organizations. “We have been in close coordination with SolarWinds, the Federal Bureau of Investigation, and other key partners,” FireEye CEO Kevin Mandia wrote in a blog post. “We believe it is critical to notify all our customers and the security community about this threat so organizations can take appropriate steps.”

More than 300,000 customers globally use SolarWinds products, according to its website. This includes more than 425 of the U.S. Fortune 500, all 10 of the top 10 U.S. telecommunications companies, all five branches of the U.S. military, the Pentagon, State Department, National Security Agency, and office of the president, among other U.S. departments.

The timing of the breach is especially worrisome, SonicWall CEO Bill Conner wrote in an email to SDxCentral.

“The news of the attack on U.S. Treasury and Commerce departments, and other government agencies, is especially troubling given major events that have captivated the attention of all Americans including the historic effort to administer a COVID-19 vaccine to the United States’ most vulnerable citizens, the 2020 presidential election, and the onboarding of new political players to the government’s highest ranking offices,” Conner wrote. “The hackers, most likely Russian backed, appear motivated by geopolitical control as well as monetary gain. A player in possession of valuable information and intellectual property could potentially pose a series of threats to influence or control global healthcare, enterprise, and government agencies.”